The general aim of the experiments proposed here is to understand, in terms of the responses of single cells, the control of specific motor responses by specific sensory stimuli. A great deal of evidence implicates the superior colliculus in the control of eye movements, and the sensory receptive fields of cells in the cat colliculus are quite well understood. The psychophysics of eye movements has been described in detail and recent advances have been made in the physiology of oculomotor neurons. Therefore, a study of the role of the superior colliculus in the control of eye movements provides some hope of relating the activity of cells with well-defined sensory fields to specific motor responses. Single cells will be recorded from the alert Cebus and cynomologous monkey, trained to track visual stimuli. The visual, auditory, and somatic receptive fields of each cell will be mapped. Then a search will be made for cells that fire in relation to specific types of eye movement. For example, a cell may respond only in relation to saccadic movements with a particular amplitude and direction. The role of visual and proprioceptive feedback in eye movement related responses will also be investigated. Additional studies will use restricted visual environments to elucidate the relationships between the colliculus and the visual cortex. We will study the receptive fields of cells in superior colliculus and in visual cortex that result from raising animals in a variety of visually deprived environments.